Every climber is attuned to the sound: deep, earthy, unmistakable. The slopes letting go of their weight.

“A huge, tremendous boom” is how Nick Cienski described it.

He and his wife knew they had only seconds until the wind-packed snow and sawtooth ice would reach Mount Everest’s base camp, a cluster of nylon tents and gear of teams waiting to push higher during the brief window each year when conditions are favorable to reach the world’s highest summit.

They prayed. They huddled together — thinking perhaps these were their last moments.

“We knew it was going to hit us. There was absolutely no doubt about it,” Cienski, an executive at the Baltimore-based clothing maker Under Armour, told The Washington Post. “It was so huge. We weren’t sure we were going to survive it or not.”

Officials say at least 19 other mountaineers on Everest didn’t survive as the avalanche roared down Saturday, unhinged by a monster 7.8-magnitude earthquake that has claimed more than 5,000 lives across Nepal and parts of China and India.

Cienski, 48, has remained at base camp — now a mournful sprawl of bulldozed tents and debris at 17,700 feet — to assist with the transport of the dead and injured. That has been the only mission for days.

But there still remains a chance for climbers to make summit bids despite the disaster.

Nepal’s government said it will allow expeditions on Everest to go forward. Although avalanches triggered by the earthquake swept parts of the base camp, officials said the route to the summit is less affected.

And at least 42 teams are at the base camp, waiting for the weeks in May when the winds and weather ease near the 29,029-foot peak.

In a phone interview, the director general of Nepal’s tourism department, Tulasi Prasad Gautam, said that many of the local Sherpas who didn’t get to work last year strongly support climbing this year.

A helicopter arrives to take people away from the Mount Everest base camp after an avalanche April 25. (6summitschallenge.com)

“We have spoken to the guides, we have talked to the climbers and consulted with operations personnel,” he said, “and everyone wants to continue with climbing this year.”

Following the avalanche Saturday, many of the guides and porters headed back to their villages in the Everest region. Those who are in charge of fixing ropes and ladders — referred to as the “icefall doctors” — will resume working on the route within two days.

This year, each person climbing Everest is paying $11,000 in fees — a major source of revenue for the government.

Everest knows death. Since the first recorded climbing deaths, in 1922, more than 200 have perished — with some frozen bodies remaining as silent sentinels over the decades. Sixteen Sherpas, the Nepali mountain guides, died in an avalanche last year.

But never before have so many people on Everest perished in an instant.

In a stroke of luck, Cienski and his wife, Sandi — Vancouver, B.C., natives with no children — had set up their tent on the edge of base camp as they became acclimated to the altitude.

He had been to Everest before. In 1989, he came within 600 meters of the summit. This time, he’s part of a team attempting to climb Everest and five more of the world’s highest peaks over the next year — called the 6 Summits Challenge — to raise awareness for human trafficking through the nonprofit group Mission 14.

It’s also a chance to test extreme-weather clothing manufactured by Under Armour, where Cienski is senior director of special projects and innovation. Sandi Cienski, a 48-year-old artist, planned to remain at base camp.

They were in their tent watching the television legal drama “Damages” when they heard the sound. “Holy crap,” Cienski recalled thinking. Then they saw the wall of white rise above them against the ice-laced rocks and steel-gray clouds.

“It was huge,” he said. “It was hundreds and hundreds of meters wide. It’s like a tidal wave, a tsunami. It was the same idea.”

The tent began to shake. Its sides were slapped by the onrushing snow. But luck had put them on the outer edge of the avalanche zone.

“It sounded like a freight train right next to your head,” Cienski recalled. “It was deafening . . . like the world was coming to an end.”

When it was over, they checked themselves for injuries. Nothing serious. They weren’t buried. Can you breathe? he asked Sandi. Good. So can I.

They clawed themselves out. Around them, survivors were walking around dazed.

Other parts of the camp were wiped away.

“Completely decimated. Zeroed out. Not one tent left standing,” he said.

They dug for survivors, stopping every few moments to listen for muffled cries, and tending to the wounded as best they could.

Cienski said he would have to meet with his team, including the Sherpas, on whether to continue the climb.

But he said the disaster has forged, in his mind, an extra determination. “It’s created a sense of resolve to get this summits challenge done successfully,” he said.

In 1989, he had climbed the mountain on a different route. But as he prepared a final push to the summit on the North Face, Cienski lost one of his boots and had to turn back. Several days later, an avalanche swept down the West Ridge, killing two members of his climbing team.

“Had I not lost my boot, I would have been in that group,” Cienski said, “[and] most likely would not have survived.”

Murphy reported from Washington. Anup Kaphle in Washington contributed to this report.

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What it takes to climb Everest

Close Everest? Some think so.

Today’s coverage from Post correspondents around the world